EP0445741B1 - Eine Methode zur Einstellung der Betriebsbedingungen von optischen integrierten Bauteilen - Google Patents

Eine Methode zur Einstellung der Betriebsbedingungen von optischen integrierten Bauteilen Download PDF

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Publication number
EP0445741B1
EP0445741B1 EP91103328A EP91103328A EP0445741B1 EP 0445741 B1 EP0445741 B1 EP 0445741B1 EP 91103328 A EP91103328 A EP 91103328A EP 91103328 A EP91103328 A EP 91103328A EP 0445741 B1 EP0445741 B1 EP 0445741B1
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EP
European Patent Office
Prior art keywords
further layer
optical
operation characteristics
refractive index
layer
Prior art date
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Expired - Lifetime
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EP91103328A
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English (en)
French (fr)
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EP0445741A1 (de
Inventor
Claudio Caldera
Carlo De Bernardi
Salvatore Morasca
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Agilent Technologies Inc
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CSELT Centro Studi e Laboratori Telecomunicazioni SpA
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method
    • G02B6/132—Integrated optical circuits characterised by the manufacturing method by deposition of thin films

Definitions

  • the present invention concerns technological methods of manufacturing integrated optical devices and more particularly it refers to a method of adjusting the operation characteristics of integrated optical devices, formed by a network of optical waveguides manufactured on or in the surface of a substrate wherein light signals are to be propagated, said method being carried out by depositing a further layer of transparent material on a surface area at which one or several optical waveguides of a completed optical device are exposed and by selecting the thickness of the further layer so as to adjust the operation characteristics.
  • the manufacturing refuses highly affect the final cost. Hence it can be convenient to adjust the optical characteristics of the obtained device to return its performance within the required specifications.
  • the device is made of electrical-field-sensitive material, e.g. of lithium niobate (LiNbO3), or of certain semiconductor materials, its optical characteristics modification can be obtained by using the method described in the paper entitled “Waveguide Electrooptic Modulators” by Rod C. Alferness, issued on page 1121 of IEEE Transactions on Microwave Theory and Techniques, August 1982.
  • suitable electrodes are placed on the device for applying a potential difference of convenient value.
  • Said potential difference generates an electrical field permitting a change in the optical characteristics of the device in its operation phase.
  • the method requires further steps in the technological process of fabrication to manufacture the electrodes and, once the device is fabricated, it requires permanent application of a voltage of controlled value, even though the operation conditions are always the same.
  • a deposition of a transparent layer of corning glass on the optical guides of an integrated optic power divider is described, deposited in order to adjust the power distribution by selecting a determined thickness of the cladding layer.
  • the refractive index of the cladding layer is higher than that of the optical guide, what implies the possibility that the coating layer guides the light radiation which thereby could propagate in different directions causing optical losses, while the adjustment possibilities are rather restricted.
  • the present invention is characterised in that further the refractive index of the further layer is lower than that of said optical waveguides and that the extension of the further layer along the light propagation direction, is selected so as to adjust the operation characteristics, wherein the thickness of the further layer is to be chosen greater than a certain minimum value of the order of some wavelengths of the light signals to be propagated in the waveguides.
  • a 3 dB beam splitter is considered; it operates on the basis of the bimodal interference principle.
  • the incoming optical signal is to be exactly divided in half between the two output branches. If the obtained device does not perform exactly the partitioning required, it is possible to intervene with the present correction method and make the changes necessary to meet the required operation specifications.
  • the splitter shown in Fig.1 consists of two input single-mode guides, with input gates P1 and P2, which join through an Y-connection into a segment of bimodal guide of length L and width W. At the end of the bimodal guide segment there is an Y beam splitter entering two output single-mode guides, with output gates P3 and P4.
  • This kind of device can operate equally well by exchanging the input gates with the output ones. Besides, either an only signal to be split exactly into two parts or two signals can be sent to the inputs, one per each input gate, when one wishes to combine them with one another and extract at the output the two halves of the obtained combination.
  • the latter method can be used in a coherent receiver, when the locally-generated signal is to be combined with the signal received to effect its detection.
  • Optical waveguides forming the device can be manufactured by epitaxial growth of a ternary or quaternary semiconductor material, such as InAIAs, InGaAIAs or InGaAsP, on a substrate of InP:Fe, denoted by SU in Fig.1. Afterwards the required guiding network is obtained by masking the grown substrate and by chemical etching the uncovered parts.
  • a ternary or quaternary semiconductor material such as InAIAs, InGaAIAs or InGaAsP
  • the beam splitter operation is as follows.
  • the optical signal is sent to an input gate, e.g. P1, and covers the single-mode guide segment.
  • an input gate e.g. P1
  • P1 an input gate
  • both the fundamental and the first higher mode are excited, wich interfere with each other.
  • a periodical spatial oscillation of the light intensity occurs, with a sequence of maxima and minima along the length L of the bimodal guide.
  • the period of this oscillation depends on the difference between the effective refractive indices of the two modes, which depends in turn on the guide geometric characteristics, width and length, as well as on the refractive indices of the various materials forming the whole guiding structure more particularly on the refractive index of the substrate, of the guiding layer and of the material which possibly covers the latter layer.
  • the oscillation phase assumes a convenient value at the output end of the bimodal segment, in the subsequent Y-splitter and in the two single-mode output guides one exactly obtains half the power available in the input guide, possible losses excepted.
  • the oscillation phase at the Y-splitter of course depends on length L of the bimodal segment, which hence is to be manufactured with rather stringent tolerances.
  • the technological process inaccuracy can be overcome by depositing on the surface,whereupon the optical guides are manufactured, once completed the normal fabrication process, a further transparent material layer.
  • This covering layer which is transparent not to increase the guide losses, is to be homogeneous, is to present a convenient refractive index and whatever thickness, provided the thickness is greater than a certain minimum value, generally of the order of some wavelengths of the processed radiation.
  • This operation causes changes in the propagation constants of guided modes which depend on the values of the refractive indices of all the materials forming the waveguide structure, and more particularly on the refractive indices of the substrate, of the guiding layer proper and of all the possible upper and lateral boundary layers.
  • the covering layer refractive index and keeping unchanged the refractive index of all the other layers one can change within a significant and useful interval the effective refractive indices in the bimodal guide and hence the period of the oscillation caused by the interference.
  • an adjustment can be carried out by depositing a covering layer with a value of the refractive index apt to bring the guiding structure to the operation point.
  • the materials used are generally to present a refractive index lower than that of the optical guide to be adjusted and can consist of resins, polymers, organic or inorganic materials, which can be deposited by whatever method.
  • the correction of a certain partitioning error can be performed not only by covering the whole optical guide with a layer of material with a suitable refractive index in function of the correction entity, but also by varying the length of the bimodal guide segment covered. In this way the setup of different deposition conditions and techniques, which depend on the material used for the correction, can be avoided.
  • Fig. 2 shows a cross section of an intermediate zone of the device, wherein it is shown a simple sequence of layers forming the guiding structure, the substrate SU, the bimodal guide and correction layer SA.
  • the bimodal guide which is 200 ⁇ m long, with a material having a refractive index equal to 1.5, a power splitting error of 47% on a branch and 53% on the other can be corrected.
  • the method above can be used to adjust the optical characteristics of other devices, e.g. directional couplers or DFB lasers (Distributed Feedback Bragg), fabricated with the above-mentioned materials or with other materials used in the integrated optics domain, such as glass, LiNbO3,SiO2, polymers, and the like.
  • DFB lasers distributed Feedback Bragg

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Integrated Circuits (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)

Claims (2)

  1. Verfahren zum Einstellen der Betriebscharakteristiken von integrierten optischen Bauteilen, die durch ein Netzwerk von Lichtleitern gebildet werden, welche auf oder in der Oberfläche eines Substrats hergestellt werden und in denen man Lichtsignale fortschreiten läßt, wobei das Verfahren durchgeführt wird durch Aufbringen einer weiteren Schicht aus transparentem Material (SA) auf einer Oberseitenfläche, an der ein oder mehrere optische Wellenleiter eines fertiggestellten optischen Bauteils freiliegen, und durch Wählen der Dicke der weiteren Schicht so, daß die Betriebscharakteristiken eingestellt werden, dadurch gekennzeichnet, daß weiterhin der Brechungsindex der weiteren Schicht niedriger ist als der der optischen Wellenleiter und daß man die Ausdehnung (M) der weiteren Schicht in der Lichtfortschreitungsrichtung so wählt, daß die Betriebscharakteristiken eingestellt werden, wobei die Dicke der weiteren Schicht (SA) höher zu wählen ist als. ein bestimmter Mindestwert in der Größenordnung einiger Wellenlängen der Lichtsignale, die in den Wellenleitern fortschreiten sollen.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Brechungsindex der weiteren Schicht entsprechend der Einstellung, der das Bauteil zu unterwerfen ist, gewählt wird.
EP91103328A 1990-03-07 1991-03-05 Eine Methode zur Einstellung der Betriebsbedingungen von optischen integrierten Bauteilen Expired - Lifetime EP0445741B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT6715790 1990-03-07
IT67157A IT1240124B (it) 1990-03-07 1990-03-07 Metodo per ritoccare le caratteristiche di funzionamento di dispositivi ottici integrati.

Publications (2)

Publication Number Publication Date
EP0445741A1 EP0445741A1 (de) 1991-09-11
EP0445741B1 true EP0445741B1 (de) 1995-01-11

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EP91103328A Expired - Lifetime EP0445741B1 (de) 1990-03-07 1991-03-05 Eine Methode zur Einstellung der Betriebsbedingungen von optischen integrierten Bauteilen

Country Status (6)

Country Link
US (1) US5139556A (de)
EP (1) EP0445741B1 (de)
JP (1) JPH04218003A (de)
CA (1) CA2037631C (de)
DE (2) DE69106551T2 (de)
IT (1) IT1240124B (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5359682A (en) * 1990-03-07 1994-10-25 Cselt-Centro Studi E Laboratori Telecomunicazioni S.P.A. Method of adjusting the operation characteristics of integrated optical devices
FR2725795A1 (fr) * 1994-10-13 1996-04-19 Corning Inc Dispositif achromatique en optique integree
US7000434B2 (en) * 2000-12-19 2006-02-21 Intel Corporation Method of creating an angled waveguide using lithographic techniques
WO2023026239A1 (en) * 2021-08-26 2023-03-02 DustPhotonics A waveguide photo detector integrated with a plurality of optical feeding waveguide ports

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3873339A (en) * 1972-03-30 1975-03-25 Corning Glass Works Method of forming optical waveguide circuit path
US3806223A (en) * 1972-03-30 1974-04-23 Corning Glass Works Planar optical waveguide
JPS5253437A (en) * 1975-10-27 1977-04-30 Nippon Telegr & Teleph Corp <Ntt> Adjusting method for coupling length in directional optical coupler
JPS57190910A (en) * 1981-05-19 1982-11-24 Omron Tateisi Electronics Co Controlling method for coupling length of optical directional coupler
DE3341482A1 (de) * 1983-11-17 1985-05-30 Philips Patentverwaltung Gmbh, 2000 Hamburg Magneto-optische wellenleiterstruktur mit kuenstlicher optischer anisotropie
JPS60256101A (ja) * 1984-06-01 1985-12-17 Hitachi Ltd ガラス部材への光学素子形成方法
US4775208A (en) * 1986-06-06 1988-10-04 Polaroid Corporation Planar waveguide mode converter device
JPS63206709A (ja) * 1987-02-23 1988-08-26 Nippon Sheet Glass Co Ltd 埋込み型シングルモ−ド光導波路の製造方法

Also Published As

Publication number Publication date
IT1240124B (it) 1993-11-27
DE445741T1 (de) 1992-02-06
IT9067157A0 (it) 1990-03-07
US5139556A (en) 1992-08-18
CA2037631C (en) 1995-06-06
EP0445741A1 (de) 1991-09-11
JPH04218003A (ja) 1992-08-07
DE69106551D1 (de) 1995-02-23
CA2037631A1 (en) 1991-09-08
IT9067157A1 (it) 1991-09-07
DE69106551T2 (de) 1995-05-24

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